Upgrade python version

[jmsevin]

This pull request implements the migration to Python 3.14, introduces a flexible container build process, and updates several dependencies for compatibility and security. Several minor code and test improvements are included to support the transition and ensure reliability.

Python 3.14 Migration and Build Improvements

• Updated Dockerfile and docker-compose.yaml to support building with a configurable Python version (defaulting to 3.14) using the PYTHON_VERSION build argument, enabling easy rollback to Python 3.12 if needed. [1] [2] [3]
• Changed the required Python version in pyproject.toml to >=3.12,<3.15 and updated key dependencies (torch, torchvision, numpy, langsmith) for Python 3.14 compatibility. [1] [2] [3]

Code and Test Adjustments for Compatibility

• Refactored src/app/services/sql_db/sql_service.py to defer database engine creation until session use, improving startup flexibility in the new Python environment.
• Updated test mocks in test_abst_chat.py and test_pdf_extractor.py for improved async compatibility and correctness under Python 3.14. [1] [2] [3] [4]

Minor Code Cleanup

• Removed an unused blank line in src/app/shared/infra/tracing.py.

[Copilot]

Pull request overview

This PR upgrades the service’s runtime and build tooling to support Python 3.14 (while keeping rollback compatibility with Python 3.12), updates key Python dependencies accordingly, and adds an operational runbook + baseline tooling to support safe rollout.

Changes:

• Make container builds configurable via PYTHON_VERSION (default 3.14) in Dockerfile and docker-compose.yaml.
• Update pyproject.toml Python constraint and bump several dependencies for compatibility/security.
• Add migration runbooks/scripts and adjust a few tests + SQL session initialization behavior to better support the migration.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Dockerfile	Adds PYTHON_VERSION build arg and uses it for base images to enable easy Python version switching.
docker-compose.yaml	Forwards PYTHON_VERSION as a build arg with a default of 3.14 for local/dev parity.
pyproject.toml	Updates supported Python range and bumps core dependencies for the migration.
src/app/services/sql_db/sql_service.py	Defers singleton DB engine/session factory instantiation until the first session request.
src/app/tests/services/test_abst_chat.py	Fixes async mocks to return correct values and improves stream/non-stream mock behavior.
src/app/tests/services/test_pdf_extractor.py	Adjusts HTTP response mocking to match the sync .json() usage in implementation.
src/app/shared/infra/tracing.py	Removes an unused blank line (cleanup).
migration/python-3.14/phase0-baseline.md	Documents a Python 3.12 baseline snapshot to compare against post-migration.
migration/python-3.14/phase0_collect_baseline.sh	Adds a script to automate baseline lint/test/startup checks and artifact capture.
migration/python-3.14/phase4-cutover.md	Documents container cutover and rollback build/tagging procedures.
migration/python-3.14/phase5-rollout.md	Provides a rollout/observability/rollback runbook for staged + production deployments.

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